Internal jugular vein phlebectasia:

The internal jugular vein in this Color Doppler image shows mild dilatation in its proximal part.
The transverse section shows marked turbulence in this vein, which is unusual, and suggests some intrinsic pathology which in this case is the large diameter of the vein. Note that the vein is far greater in size than the Common carotid artery near it. You can read more on this topic by scrolling down to the case and images at:
http://www.ultrasound-images.com/vascular.htm